I have to disagree strongly with this, as we’re talking about differences of degree and not kind; the unique status of Peurto Rico is literally the result of a racist law effectively preventing non-whites from becoming US citizens: https://en.m.wikipedia.org/wiki/Naturalization_Act_of_1790
This law was finally repealed...in the 1950s, decades after the US claimed the territory as spoils of war, and the 1917 act that gave them quasi-citizenship. It is in truth just a facsimile of true US citizenship, because congress can revoke it and they are not allowed to vote in presidential elections while residing in their home territory. No citizen residing in Texas or Hawaii would consider that remotely fair, because it isn’t.
The US is an unusual case in the history of empires, because it was a colonial power that seems to downplay that fact publicly. Perhaps that is because it doesn’t fit with the national mythos. Whatever the reason, part of the legacy is having different degrees of citizenship based on race and geography that must eventually be reconciled one way or the other.
Per wikipedia's interpretation of The Immigration and Nationality Act of 1952, Guamanians are US citizens at birth: https://en.wikipedia.org/wiki/Voting_in_Guam#U.S._citizenshi...
The US system does not raise the same concerns about racism. There are different political subdivisions in the US with different relationships with the federal union. For example, those in Puerto Rico don’t pay federal taxes. Washington DC has no independent sovereignty, unlike the states, etc. But those distinctions aren’t based on race or nationality (everyone is a US national). And in many respects they are mutual decisions. Puerto Rico has repeatedly rejected ballot measures to become a state. If a Puerto Rican person wants to vote in US elections, they can just move to any other political subdivision of the US that is a full state.